Since new applications and upcoming standards require increasing data rates and lower power consumption, the study and development of new architectures of communication transmitters for user units is very active. In modern wireless digital communication standards (cellular, connectivity, etc.) the baseband signal to be transmitted has a complex nature. In these standards each sample of the signal to be transmitted is equivalent to the coordinates of a point in a two dimensional plane. Consequently, the alternative transmitter architectures used in practice correspond to alternative ways of expressing the point coordinates, namely in Cartesian coordinates, or in Polar coordinates, or as a combination of Cartesian and polar coordinates, or as a sum of two simple constant amplitude vectors (phasors).
In a typical wireless transmitter that uses I-Q modulation, an input data comprises an in-phase component and a quadrature component. The I-Q transmitter comprises a DAC, for example an RFDAC that convert the in-phase and the quadrature components to a pair of I and Q output signals. RFDACs directly convert a digital baseband signal into an RF output signal, by using a building block which combines digital-to-analog conversion and up conversion mixing. High-performance digital-to-analog converters with high resolution can provide the flexibility needed to support multiple frequency bands and multiple standards in modern wireless communication transmitters. For cellular applications such as WCDMA or LTE, the required resolution of DACs is typically in the range of 15 bits. However, the high resolution DACs lead to higher power dissipation and implementation area.